Our mast base is severly compressed and water is showing up everywhere below. I have found a recent thread regarding repairs, so I know that the raised section has to be cut out and also some of the cabintop skin and core below will need removal and repair. But why a "T" shape? My inclination is to go back with a simpler shape, one that raises the mast base above the surrounding deck and allows room for a wiring conduit, but is oval or even a rectangle. Also, I tried to save another thread about this repair a year or so ago. Unfortunately, when I saved it in Thread Tracker, something happened and it never appeared. That repair suggested using a monel or delrin plate instead of aluminum when building up the section between the compression post and the mast base. Does anyone remember that discussion?
Why "T" shape at mast base?
- Thread starter David Popken
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J
Jim
Which boat?
Which boat are you talking about? If it is the H-31 or 34. It is not that bad I fixed mine and didn't do any of what you mentioned. Write back and give us more info.
Which boat are you talking about? If it is the H-31 or 34. It is not that bad I fixed mine and didn't do any of what you mentioned. Write back and give us more info.
Replacing wood in the mast step
When water gets to wood, it rots. In rebuilding the mast step, we took the opportunity to replace the wood in the sandwich. The ideal material would be: - Incompressible to carry over two tons of static compression from the mast (more in dynamic loading.) - Impervious to the long term effects of water. - Stiff to spread the compression load over a broader area. - Easy to shape and fast setting during the rebuild. - Low cost. - Light (not a big factor). Our original idea was to just use epoxy. But we realized how long it would take to set up in the massive thickness required. Aluminum is an obvious choice on all counts. The only negative is that its stiffness meant it wouldn't easily bend to fit the curvature of the deck. So we made a flat surface of epoxy to bed it on, and built up the curve with epoxy and fiberglass on the top. I don't know the comparable compressibility and stiffness of monel or delrin - we didn't consider either. I think the "T" shape is just the designer's whim. Maybe it provides the increased thickness and stiffness versus the principal directional stresses from the mast. (Fore and aft, and side to side. Just a guess!) Do let us know what model you are talking about! Good Luck, David LAdy Lillie
When water gets to wood, it rots. In rebuilding the mast step, we took the opportunity to replace the wood in the sandwich. The ideal material would be: - Incompressible to carry over two tons of static compression from the mast (more in dynamic loading.) - Impervious to the long term effects of water. - Stiff to spread the compression load over a broader area. - Easy to shape and fast setting during the rebuild. - Low cost. - Light (not a big factor). Our original idea was to just use epoxy. But we realized how long it would take to set up in the massive thickness required. Aluminum is an obvious choice on all counts. The only negative is that its stiffness meant it wouldn't easily bend to fit the curvature of the deck. So we made a flat surface of epoxy to bed it on, and built up the curve with epoxy and fiberglass on the top. I don't know the comparable compressibility and stiffness of monel or delrin - we didn't consider either. I think the "T" shape is just the designer's whim. Maybe it provides the increased thickness and stiffness versus the principal directional stresses from the mast. (Fore and aft, and side to side. Just a guess!) Do let us know what model you are talking about! Good Luck, David LAdy Lillie
The boat in question is a 1978 H30
I'm going to take a picture of the mast base and attach it later.
I'm going to take a picture of the mast base and attach it later.
J
John
I'm not done yet.....
I had posed this same question for the same reasons last fall. Tried Hunter also, but no one seems to know why it's the T shape. I believe 2 things: 1) because the core under the mast step was balsa, and the actual "T" was cored with plywood, the "T" shape was necessary for stiffness. 2) It made a nice platform to mount turning blocks. That being said, if your mast step is as compressed as you say, and there is that much water intrusion, it should be very easy to get the deck off in one piece with the "T" intact. Making it easy to just replace the "T" as it originally was. Update on my project. In my case, I cut out the top layer of deck, preserving the "T" shape, which was separately un-"cored" from the top. I replaced all the rotten balsa and built up a 10" X 12" area of fiberglass cloth directly under the mast. It was in this area that David used the aluminum, but I had already started with glass when I posted the question. I was worried about replacing the skin ( with the "T") for a number of reasons not necessary here. The end of it was that I replaced the skin as one whole piece, and then ensured solid adhesion to the balsa core ( and smooth edges ) by using 3/4" plywood strips, which I bolted thru and tightened down enough to hold, but not squeeze all the epoxy out. The result was very good, I feel confident that the deck skin is well adhered. I sanded out my 12:1 "V" along the cut edges ( the worst part of the whole job ) and got that all cleaned up and ready to go, then I had to cover the boat for the winter because I was going out of town for a week. Been too cold to do anything since. So I am still left with the task of laying the glass to tie the seams together, and then re-coring and then finishing the "T". I am looking into getting a piece of aluminum to core the "T" with. David is absolutely right, building up that thickness with glass is very time consuming. Good luck
I had posed this same question for the same reasons last fall. Tried Hunter also, but no one seems to know why it's the T shape. I believe 2 things: 1) because the core under the mast step was balsa, and the actual "T" was cored with plywood, the "T" shape was necessary for stiffness. 2) It made a nice platform to mount turning blocks. That being said, if your mast step is as compressed as you say, and there is that much water intrusion, it should be very easy to get the deck off in one piece with the "T" intact. Making it easy to just replace the "T" as it originally was. Update on my project. In my case, I cut out the top layer of deck, preserving the "T" shape, which was separately un-"cored" from the top. I replaced all the rotten balsa and built up a 10" X 12" area of fiberglass cloth directly under the mast. It was in this area that David used the aluminum, but I had already started with glass when I posted the question. I was worried about replacing the skin ( with the "T") for a number of reasons not necessary here. The end of it was that I replaced the skin as one whole piece, and then ensured solid adhesion to the balsa core ( and smooth edges ) by using 3/4" plywood strips, which I bolted thru and tightened down enough to hold, but not squeeze all the epoxy out. The result was very good, I feel confident that the deck skin is well adhered. I sanded out my 12:1 "V" along the cut edges ( the worst part of the whole job ) and got that all cleaned up and ready to go, then I had to cover the boat for the winter because I was going out of town for a week. Been too cold to do anything since. So I am still left with the task of laying the glass to tie the seams together, and then re-coring and then finishing the "T". I am looking into getting a piece of aluminum to core the "T" with. David is absolutely right, building up that thickness with glass is very time consuming. Good luck
Did you use a circular saw
to cut out your skin? I went to your pics and the cutout was nice and neat. I had assumed that I would be rebuilding that whole area with new glass and gel coat, but your photos tell me otherwise. I noticed the chisels. Did you use those for peeling the skin away from the core? Also, I wonder if one could make the large rectangular cut, leaving the raised section untouched and remove all plywood and core from the back side, thus saving the repair on the top of the "T"? the only problem I have is that the raised section is so compressed, I don't think it will ever be flat again.
to cut out your skin? I went to your pics and the cutout was nice and neat. I had assumed that I would be rebuilding that whole area with new glass and gel coat, but your photos tell me otherwise. I noticed the chisels. Did you use those for peeling the skin away from the core? Also, I wonder if one could make the large rectangular cut, leaving the raised section untouched and remove all plywood and core from the back side, thus saving the repair on the top of the "T"? the only problem I have is that the raised section is so compressed, I don't think it will ever be flat again.
J
John
more info
I used a dremmel on the "T" shape, and that was a big waste of time. I butchered the "T", because I cut out a smaller area and then kept working my way back until I had removed the whole top of it.. My ply was soaked. To cut out the large area I did use a circular saw and that was a breeze. I did use the chisels to peel away the skin, and also used a hair dryer to heat it up. Worked very well. You need to be careful not to peel too hard so you don't crack the skin and also so it is not bent up too much for when you want to replace it. It was definitely much easier to replace the skin than to reglass the deck. As I said, I thru bolted to make sure everything fit well, so that gave me piece of mind that it all wnet back together securely. Down side was about 10 small holes in the roof inside, but I can deal with that. If your "T" is crushed down, then it's going to need to be rebuilt from the top ( IMO ). I think that is the best way to make sure it is all level etc. Rebuilding from the inside out would require that you rebuild it before replacing the skin, and that leaves you open for issues involving level, square, gaps under the "T", curve of the deck etc. One thing to note is that it's not level or even under there. By that I mean that there is not a uniform thickness of balsa coring. It varies, and the deck is both curved on top but in some cases flat underneath. This leads to areas where the deck skin was not originally actually in contact with the balsa core. This was in particular at the ends of the "T", where there are hollow areas about the size of a pack of cigarettes. This unfortunately allows any water that has leaked in to travel over the top of the balsa and rot it's way back from the top. This is another reason why it would be very difficult to rebuild the "T" from underneath. I cut the "T" core out, and left the lip alone. When I finish re-coring, I will re-glass and use the lip to make sure everything is level etc . I could possibly look better by doing it inside out, but leaves more room for error. Also for sanding the "V", I bought a circular sander and that was useless ( I don't know why ). I wasted a lot of time with that before getting an attachment for my drill, and it was done in about an hour.
I used a dremmel on the "T" shape, and that was a big waste of time. I butchered the "T", because I cut out a smaller area and then kept working my way back until I had removed the whole top of it.. My ply was soaked. To cut out the large area I did use a circular saw and that was a breeze. I did use the chisels to peel away the skin, and also used a hair dryer to heat it up. Worked very well. You need to be careful not to peel too hard so you don't crack the skin and also so it is not bent up too much for when you want to replace it. It was definitely much easier to replace the skin than to reglass the deck. As I said, I thru bolted to make sure everything fit well, so that gave me piece of mind that it all wnet back together securely. Down side was about 10 small holes in the roof inside, but I can deal with that. If your "T" is crushed down, then it's going to need to be rebuilt from the top ( IMO ). I think that is the best way to make sure it is all level etc. Rebuilding from the inside out would require that you rebuild it before replacing the skin, and that leaves you open for issues involving level, square, gaps under the "T", curve of the deck etc. One thing to note is that it's not level or even under there. By that I mean that there is not a uniform thickness of balsa coring. It varies, and the deck is both curved on top but in some cases flat underneath. This leads to areas where the deck skin was not originally actually in contact with the balsa core. This was in particular at the ends of the "T", where there are hollow areas about the size of a pack of cigarettes. This unfortunately allows any water that has leaked in to travel over the top of the balsa and rot it's way back from the top. This is another reason why it would be very difficult to rebuild the "T" from underneath. I cut the "T" core out, and left the lip alone. When I finish re-coring, I will re-glass and use the lip to make sure everything is level etc . I could possibly look better by doing it inside out, but leaves more room for error. Also for sanding the "V", I bought a circular sander and that was useless ( I don't know why ). I wasted a lot of time with that before getting an attachment for my drill, and it was done in about an hour.
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